Abstract This proposal is to establish a recruitment, data collection and collaborative research site in Wisconsin for the multi-site Study to Explore Early Development (SEED) of autism spectrum disorder (ASD) of the Center for Disease Control and Prevention (CDC). The overall goals of the SEED are to: characterize phenotypic variability and identify relatively homogeneous subgroups of ASD; and investigate risk factors for ASD by comparing the early exposures and development of well-characterized ASD cases and controls selected to represent diverse population subgroups. The specific aims of this project are to: (1) implement the SEED 3 protocol in a 20-county catchment area (4,015 births in 2014) in south and central Wisconsin that encompasses the Wisconsin Autism and Developmental Disabilities Monitoring (ADDM) Network catchment area where surveillance of ASD and other developmental disabilities as part of CDC's ADDM Network has been underway since surveillance year 2002; (2) to enhance recruitment and achieve enrollment and data collection targets for 375 children and their pares, as specified in the SEED 3 protocol; (3) submit data and biospecimens collected according to the SEED 3 protocol to the Centers for Autism and Developmental Disability Research Epidemiology (CADDRE) Data Coordinating Center and SEED Central Laboratory and Biosample Repository, respectively; and (4) collaborate with other CADDRED members and actively participate in relevant CADDRE workgroups, data analysis and preparation of manuscripts, including at least five manuscripts to be led by the Wisconsin SEED research team. This research will generate new knowledge of the risk factors for and potential prevention of ASD, a leading category of disability among children, with effects across the lifespan.